Manufacture of paper



Patented June 16, 1931 UNITED. STATES PATENT OFFICE HAROLD ROBERT RAFTON, OF LAWRENCE, MASSACHUSETTS, ASSIGNOR TO RAFFOLD PROCESS CORPORATION, A CORPORATION OF MASSACHUSETTS MANUFACTURE or PAPER No Drawing.

This invention relates to the manufacture of paper.

The principal object of my invention is to provide a method whereby paper may be manufactured to contain an amount of filler greater than is feasible by the usual procedure.

An important object is to provide a method whereby in the papermaking operation a smaller proportion of the filler than is normal passes thrugh the web-forming device into the white water.

A further object is to provide a method whereby paper of very high filler content may be manufactured.

Other objects and advantages of my invention will become apparent in the course of the following description.

The ordinary method of manufacturing paper is to mix the fibre and filler in the beater or like machine, together with alum,

- or alum and size, and then after suitable treatment in the beater, to pass the mix through the subsequent apparatus and mechanical treating equipment such as the chests and the jordan, and then to dilute the mix at the mixing box with white water, e. g. tray water from the machine, and with other water if desired, and finally'to conduct the, diluted mix to the web forming device of the paper machine. Here the web is formed with simultaneous removal of the white water, which normally contains a relatively larger proportion of filler to fibre than does the stock fed to the web-forming device.

The retention of filler in paper has always been a matter for serious consideration in papermaking. In the former prevailing practice, which has now beensuperceded toa considerable extent, practically all of the vwhite water (excepting part of the tray water) flowed to waste and hence a considerable proportion of the filler employed in the beater escaped in the white water and was lost. This condition was greatlyifn proved by the introduction of save-all sys tems, such as by sedimentation, filtration,

deckering, or the like which usually recover a large proportion, .and in some cases practi- Application filed November 27, 1928. Serial No. 322,292.

cally all, of the solidssuspended'in the white water.

Such save-all systems usually return the recovered stock to the beater or to one of the chests for re-use in the cycle. This practice has thus eliminated to a considerable extent the wastage of filler. It has consequently reduced the amount of filler required to be used in the beater for a given filler content in the paper. Moreover it has provided a means by which a relatively higher percentage of filler in the finished paper may be obtained in regular commercial production than was former ly feasible, as it is now possible to carry a higher percentage of filler to fibre circulating in the machine waters without excessive losses. j

' Howevereven with the present'save-all systems there is a practical limit to which the filler content of paper may be raised for any given set of conditions. the fact that when the filler content of the stock is pushed beyond a certain. point the paper web will not hold appreciably more filler, and more over under these conditions the save-all systems rapidly become inef- This results from ficient and fail to recover the greatly increased filler content of the white water.

For instance in magazine paper, with asul-, phite-soda furnish, with several hours beating, and machine speed between 350 and 400 feet per minute, using a sedimentation save= all system, the filler content runs about 22% as a maximum. With afurnish consisting of approximately equal parts of sulphite pulp, soda pulp and old paper stock with from 1 to 2 hours beating, with a machine speed of ap proximately 400 feet per minute, using a filtration save-all system, the filler content runs about 24% as a maximum.

It will be understood, of course, that with varying conditions of h dration of the stock, and varying kinds of fi re and grades of pa per to be made aswell as varying machine speeds, amounts of sizing, alum, and the variation of the numerous other factors in'papermaking, that the. filler content in any given case may varysomewhat one way or the other, but in making, for instance, a magazine grade of paperthe above represent approximately the maximum filler contents which can be obtained in regular machine operation.

I have discovered that it is possible to increase the filler content of paper above that percentage normally obtainable when the usual method is employed, by the expedient of adding the filler to the paper mix which already contains alum at or subsequent to the point at which the paper mix is diluted prior to delivery to the web-forming device, i. e. in other words at the wet end of the paper machine.

I have found for instance that a given amount of filler added in the beater to a fibrous mix containing alum will not produce a paper having as high a filler content as will an equal amount of filler added at the wet end of the paper machine to a similar fibrous mix containing alum. The difference -may range from as low as 1% in some cases up to 3 or 4% in other cases, and in still other cases the difference in percentage may be much higher; Even the lower mentioned difference of 1% is of great economic importance, amounting to a saving of $30.00 to $50.00 per day in a 100 ton mill (assuming no change in fibre furnish), and of course the saving mounts proportionately with the increase of the difference in filler content that it is possible to obtain.

Of course part of the filler may be added in the beater and part at the wet end of the paper machine but I have found that the maximum results are obtained by the addition of all the filler. at the wet end of the paper machine.

In the practice of 'my invention my preferred method is to add the fibrous materials and alum, together with the size if any is to be employed, in the beater, subject the mix to the usual mechanical treatment, then pass it through the usual steps and mechanical treating machinery up to the point at which it is to be diluted prior to delivery to the webforming device. At or subsequent to this point I add the requisite amount of filler, preferably continuously,preferably in dilute aqueous suspension, either in fresh water, or

admixed with a diluting liquid.

I have found that if filler be added when the fibrous mix containing the alum is in relativelywoncentratcd condition, even after it has left the beater,'and particularly in places where the mix would be subjected to application Sena-l No. 322,291,.filed Novemagitation such as is normal in stuff chests, this effect of increased filler retention is de teriorated, and thus to procure the effect it is necessary to add the filler under such con- .ditions that there is a minimum of intimacy as well as time of contact of the constituents of the mix, namely, at the wet end of the paer machine. I have also found that prolbnged agitation even in dilute state injures the effect, but from a practical standpoint-the time that the mix remains in the dilute condisize may also be added at the wet end of the paper machine, but the important point is that the filler must be added at this point and I therefore consider the addition of the alum and/or size together with the filler at this point the equivalent of. adding the alum and/or size to the fibre in the beater. I have not found that the presence of sizing has any marked effect on the filler retention where my process is employed. The addition of the filler in the dilute stage seems to be the controlling factor.

My process results in a greater retention of filler inthe paper and hence, under any given set of circumstances, in a smaller amount of filler passing through into the white water, with a corresponding lessened difficulty in operating save-all systems. Of course, to obtain a higher filler content in the paper than formerly, where a substantially .closed white water cycle is employed, more filler in proportion to should be used.

In the above description of my preferred ractice I have assumed a use of alum in the eater no greater than that regularly'employed under any given set of conditions. However, I have found that it is sometimes very desirable to increase this amount of alum and thereby still further increase the percentage of filler retained in the paper. The saving obtained by increased filler content normally more than ofisets the increased alum cost. This increased use of alum in thebeater is indicated up to the point where other factors negative the desirability of further-increased filler content suchas strength, twosidedness, or the like. The amount of extra fibre than formerly alum which is desirable to be added may also be limited to some extent the desire not to getthe stock too acid.

Although not essential to the practice of my process I prefer to return the concentrated material recovered from the white water to the wet end of the paper machine rather than to the paper mix at any point in which 1 the'mix is in relatively concentrated condition, as by this procedure the desired increased filler effect will be enhanced.

Cross reference is made to my copending.

ber 27, 1928. in which a similar increased filler retention effect is obtained by the addition of alum at the wet end of the paper machine to plication just referred to, which would com-.

prise the addition of both the filler and the alum at the wet end of the paper machine to v concentrated condition, such as in the beater or stuff chests.

Instead of alum, I may use other salts of aluminum such as the chloride, or with a certain measure of success, other metallic salts such as zinc salts, for example zinc sulphate.

By the word filler I means such inorganic loading as clay, talc, or the like, which is insoluble in water and substantially chemically inert to the materials ordinarily employed in paper-making, such for example as alum.

By the words filled paper I means paper filled with material coming under the defini tion of the word filler given above.

When I use the word paper herein, I use it in the broad sense to include products of manufacture of all types and of all weights and thicknesses, which contain as an essential constituent a considerable amount of prepared fibre and which are cap-able of being produced on a Fourdrini er, cylinder, or other forming, felting, shaping or molding ma chine. A

By the term wet end of the paper machine I intend to include those instrumentalit ies employed in paper manufacture by which and/or in which a relatively concentrated paper mix is diluted, and treated, conveyed orfed up to the point of Web-formation, such as the mixing box, regulating and proportioning devices, rifllers, troughs, screens, head boxes, inlets, and the like.

While I have described in detail the pre-,

ferred embodiment of my invention, it is of course to be taken as illustrative only and not limiting, as it is to be understood that details of procedure, kinds of material used in.

- taining a metallic salt under conditions favoring the minimizing of time of contact, and thereafter making paper therefrom.

2. The method of producing filled paper, comprising adding filler to a fibrous mix containing a metallic salt under conditlons favoring the minimizing of intimacy and time of contact, and thereafter making paper therefrom.

3. The method of producing filled paper, comprising adding filler at the wet end of the paper machine to a fibrous mix to which a metallic salt has been previously added, and thereafter making paper therefrom.

4. The method of producing filled paper, comprising adding filler at the wet end of the paper machine to a fibrous mix to which a salt of aluminum has been previously added,

and-thereafter making paper therefrom.

5. The'method of producing filled paper, comprising adding filler at the wet end of the paper machine to a fibrous mix to which alum has been previously added, and thereafter making paper therefrom.

6. The method of producing filled paper,

comprising adding filler at the wet end of the paper machine to a fibrous mix consisting of sulphite pulp and soda pulp to which a metallic salt has been previously added, and thereafter making paper therefrom.

.7. The method of producing filled paper, comprising adding filler at the wet end of the paper machine to a fibrous mix consisting of sulphite pulp, soda pulp, and old paper stock to which a metallic salt has been previously added, and thereafter making paper therefrom.

8. The method of producing filled paper, comprisingmixing fibrous material and a metallic salt in a beater, adding filler at the wet end of the paper machine, and thereafter making paper therefrom.

9. The method of producing filled paper, comprising mixing fibrous material and a salt of aluminum in a beater, adding filler at the wet end of the paper machine, and thereafter making paper therefrom.

10. The method of producing filled paper, comprising mixing fibrous material and alum in a beater, adding filler at the wet end of the paper machine, and thereafter making paper therefrom.

11. The method of producing filled paper, comprising adding fibrous material in a beater, adding filler and a metallic salt at the wet end of the paper machine, and thereafter making paper therefrom.

12. The method of producing filled paper, comprising adding fibrous material in a beater, adding filler and alum at the wet end of the paper machine, and thereafter making paper therefrom.

13. The method of producing paper, comprising adding filler at the wet end of the paper machine to a fibrous mix including size to which a metallic salt has been previously added, and thereafter making paper therefrom. I

14. The method of producing paper, comprising adding filler at the wet end of the paper machine to a fibrous mix including size to which alum has been previously added, and thereafter making paper therefrom.

15. The method of producing paper, comprising mixing fibrous material and size and a metallic salt in a beater, adding filler at the wet end of the paper machine, and thereafter making paper therefrom.

In testimony whereof I aflix my signature. r

HAROLD ROBERT RAFTON. 

